Microstructural investigation of hexagonal-shaped diamond nanoplatelets grown by microwave plasma chemical vapor deposition

Diamond crystallites in hexagonal-shaped nanoplatelet morphology were synthesized in microwave plasma chemical vapor deposition (MPCVD) system using a CH4/H2 gas mixture with a ratio of 0.667%. Diamond nanoplatelets were deposited on (1 0 0) silicon substrate. The substrate was embedded within the plasma ball close to its center where the high temperature above 1100 °C was reached during the deposition. Surface morphologies and crystalline characteristics of the deposited diamond were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM observations clearly show that the diamond nanoplatelets exhibit hexagonal-shaped morphologies, and the thickness and the length are measured to be around 20-30 nm and several hundred nanometers, respectively. Also, SEM shows that the distribution of the nanoplatelet density gradually increases from the center to the corner of the sample. TEM with selected area electron diffraction shows that each platelet is a single crystalline diamond. Both 〈1 1 0〉 and 〈1 1 1〉 orientations of the diamond platelets are observed.